Laser rangefinders are well known in the rangefinding art. A laser rangefinder emits one or more laser pulses toward an object the range of which is to be determined. The laser pulses reflect from the object back to the rangefinder, and are detected by a laser detector. The length of time between emission of each laser pulse and its detection by the laser detector is measured by a timer clock, and the range is determined from this time period. A numerical range figure may be displayed on a suitable electronic display on the rangefinder, or may be printed on a remote paper printer, for example.
Typical laser rangefinders of the prior art have three separate optical channels: a channel for the transmitting optics, a channel for the receiving optics, and a channel for the viewing optics. Each of these optical channels typically has its own distinct optical axis. A few laser rangefinders have been designed in which the receiving and viewing channels are coaxial. However, there are no known laser rangefinders with coaxial transmitting, receiving and night viewing channels. Such a rangefinder having coaxial optics for all three functions is highly desirable for reducing size, weight, and cost of the rangefinder.
A second disadvantage with laser rangefinders of the prior art resides in the lens system for focusing the viewing optics. A typical focusing system requires relative movement between the viewing lens and the transmitter and receiver optics. This relative movement between the viewing and the rangefinder optics contributes to boresight loss, parallax, and alignment stability problems in the rangefinder.
Consequently, a need exists for a laser rangefinder with an improved optical system which uses a single optical channel for transmitting, receiving and viewing functions. Preferably, such an improved laser rangefinder will have an optical system which permits focus adjustment for the viewing system without relative movement between the viewing lens and the transmitter or receiver optics. Such an improved laser rangefinder will further preferably have night vision capability.